Data field read only if not empty

Hi,
I would like to achieve this:

1) During the Registration, the form displays the Data field but is not Required.

2) if the user sets this field at the Registration then in his/her Edit Profile the Data Field must be read-only (I meant the user cannot change this value anymore but he/she can see it in the Edit Profile Form).

3) if the user didn't provide this field at the Registration, he/she can do it only once in the Edit Profile. Once he/she save the form, he/she can edit this field anymore.

How can I do this? Can you guide me to the right process?

maybe with AutoAction or what?

Thanks
N

Use CB Conditional and have the field condition it self, but you'll need to do this with a static condition. The below should work.

Display: Field conditional show
Field: Custom > Value
Custom Value: [FIELD_NAME]
Operator: Empty
Locations
Registration: No
Profile Edit: Yes
Profile View: No
Userlists Search: No
Userlists View: No

Replace FIELD_NAME with the actual name of your field. You may need to turn off value resetting for conditions though. You can do this by editing CB Conditional in CB > Plugin Management and turning of resetting under Parameters.